/Engine/Plugins/Enterprise/DatasmithImporter/Source/DatasmithImporter/Public/ObjectElements/DatasmithUObjectElements.h
Set the source UV channel that will be used at import to generate the lightmap UVs
[UFUNCTION](Programming/UnrealArchitecture/Reference/Functions)(BlueprintCallable, Category="Datasmith | Element") void SetLightmapSourceUV ( int32 UVChannel )